1. Field of the Invention
The invention relates to a polysubstituted cyclopentadiene compound, of which at least one substituent is of the formula --RDR'.sub.n, where R is a linking group between the cyclopentadiene and the group DR'.sub.n, D is a hetero atom selected from group 15 or 16 of the Periodic Table of Elements, R' is a hydrocarbon radical containing 1-20 carbon atoms (e.g., alkyl, aryl, aralkyl, and the like, including straight chain, branched, cyclic, and derivatives thereof), and n is the number of R' groups bound to D.
2. Description of the Related Art
As referred to herein, cyclopentadiene will be abbreviated as Cp. The same abbreviation will be used for a cyclopentadienyl group if it is clear, from the context, whether cyclopentadiene itself or its anion is meant.
An overview of the influence of cyclopentadiene substituents on the catalytic activity of a metal complex comprising the substituted cyclopentadiene as a ligand was provided in J. of Organomet. Chem. 1994, 479, 1-29. It was observed that the chemical and physical properties of the metal complexes can be varied by modifying the substituents on the cyclopentadiene ring. However, no predictions were made concerning the effect of the specific substituents of the invention. It was emphasized that "[a]n important feature of these catalyst systems is that tetravalent Ti centres are required for catalytic activity" (note that Ti was given as an example of a metal in the cyclopentadienyl-substituted metal complex).
Szymoniak et al., J. Org. Chem. 1990, 55, 1429-1432, disclosed a tetramethyl-substituted cyclopentadiene containing a diphenylphosphinyl group as a fifth substituent, which is coupled to the Cp either directly or via an ethylene group. The synthesis method described is highly specific, and there is no teaching whether or how, Cp compounds substituted in other ways can be obtained.
Jutzi et al., Synthesis 1993, 684, indicated that the above-described method of Szymoniak et al. mainly produces geminally substituted compounds, which cannot be used as anionic ligands in metal complexes. Geminally substituted Cp compounds are not suitable for use as a ligand and are not considered to be within the scope of the invention.
Cyclopentadiene tetrasubstituted with methyl or ethyl groups and a substituent of the formula --RDR'.sub.n, where R is a methylene or ethylene group and D is O, N or S, was disclosed in DE-A-43.03.647.
Bensley et al., J. Org. Chem. 1988, 53, 4417-4419, disclosed a tetramethyl-substituted cyclopentadiene containing a diphenylphos-phinyl group as the fifth substituent, which is coupled to the Cp via a propylene group.
Kresze et al., Chemische Berichte 1963, 666, 45-53, disclosed a bis(methoxyethyl)cyclopentadiene.
Hafner et al., Chemische Berichte 1963, 661, 52-75, disclosed a cyclopentadiene substituted with two adjacent methyl groups in combination with a dimethylamino group which is coupled to the Cp via a methylene group.
A tetramethyl-substituted cyclopentadiene containing an ethoxy group as the fifth substituent which is coupled to the Cp via a dimethylsilylene group was disclosed in EP-A-0,416,815.
A cyclopentadiene which is substituted with one tert-butyl group in addition to either a methoxy or an ethyl methoxy group was disclosed in Angew. Chem. Int. Ed. Engl. 1995, 34, 2266-2267.
Unexpectedly, it has now been found that catalyst components having high activity in the polymerization or copolymerization of .alpha.-olefins can be obtained if the Cp compounds of the invention are used singly as a ligand of a metal which is reduced. A mono-Cp-substituted metal complex with a metal in a reduced oxidation state is obtained; the Cp-containing ligand is multidentate and monoanionic. This has the advantage of strongly stabilizing the metal complex without blocking active sites of the complex, so that the complexes have excellent catalytic activity.
The metal is present in reduced form in the complex, which means that the metal is in a reduced oxidation state. As referred to herein, "reduced oxidation state" means an oxidation state which is lower than the highest possible oxidation state of the metal (for example, the reduced oxidation state is at most M.sup.3+ for a transition metal of group 4, at most M.sup.4+ for a transition metal of group 5 and at most M.sup.5+ for a transition metal of group 6).
As referred to herein, a multidentate monoanionic ligand is bonded with a covalent bond to the reduced metal at one site (the anionic site) and is bonded either (i) with a coordinate bond to the reduced metal at one other site (bidentate) or (ii) with a plurality of coordinate bonds at several other sites (e.g., tridentate, tetradentate). Such coordinate bonding can take place, for example, via D heteroatom(s). It is noted, however, that heteroatom(s) can be present without coordinately bonding to the reduced metal, so long as at least one coordinate bond is formed between the electron-donating group D and the reduced metal.
As referred to herein, a coordinate bond is a bond (e.g., H.sub.3 N-BH.sub.3) which when broken, yields either (i) two species without net charge and without unpaired electrons (e.g., H.sub.3 N: and BH.sub.3) or (ii) two species with net charge and with unpaired electrons (e.g., H.sub.3 N..sup.+ and BH.sub.3..sup.-). On the other hand, as referred to herein, a covalent bond is a bond (e.g., CH.sub.3 --CH.sub.3) which when broken yields either (i) two species without net charge and with unpaired electrons (e.g., CH.sub.3. and CH.sub.3.) or (ii) two species with net charges and without unpaired electrons (e.g., CH.sub.3.sup.+ and CH.sub.3 :.sup.-). A discussion of coordinate and covalent bonding is set forth in Haaland et al., Angew. Chem (Int. Ed.), 1989, 28, 992.
The above-mentioned documents would not enable those skilled in the art to deduce that the compounds of the invention have the particular catalytic activity described above. Corresponding complexes in which the Cp compound is not substituted in the manner described in the present application prove unstable or, if they have been stabilized in some other way, are found to provide less active catalysts than the complexes containing substituted Cp compounds of the invention, particularly in the case of .alpha.-olefin polymerization or copolymerization.
Moreover, the Cp compounds of the invention are found to be able to stabilize highly reactive intermediaries such as organometal hydrides, organometal borohydrides, organometal alkyls and organometal cations. Furthermore they prove suitable as stable and volatile precursors for use in metal chemical vapour deposition.